The present disclosure relates to the processing of substrates, such as for example, semiconductor substrates. In particular, it provides a novel method to pattern substrates utilizing self-aligned blocking and spacer self-healing techniques.
As geometries in substrate processing continue to shrink, the technical challenges to forming structures on substrates via photolithography techniques increase. This is particularly challenging for Back End of Line (BEOL) trench patterning where patterning demands of sub-30 nm pitches may exist.
A variety of techniques for addresses such challenges have been attempted. Use of extreme ultraviolet (EUV) lithography using wavelengths of 13.5 nm is one technique. However, EUV lithography raises numerous challenges including source power challenges. Another technique is directed self-assembly (DSA). However, DSA faces significant line placement roughness (LPR) challenges. Attempts have been made to achieve small pitches utilizing 193 nm lithography. Due to the limitations of 193 nm lithography, additional processing steps are required. One technique for achieving suitable photolithography for such pitches involves multiple patterning techniques to provide for pitch splitting. Such multiple patterning techniques have included self-aligned double patterning, self-aligned triple patterning and self-aligned quadruple patterning. These multiple patterning techniques may involve the utilization of sidewall spacers for defining structures at pitches that are less than the original photolithography pitch. Such techniques have allowed the extension of standard photolithography techniques without resort to EUV lithography or DSA.
For example, in double patterning techniques, sidewall spacers are utilized to increase the structure density on the substrate surface. A mandrel structure may be formed on the substrate through known photolithography techniques. Sidewall spacers may then be formed adjacent the mandrel. Removal of the originally patterned mandrel leaves the two sidewall spacers, thus forming two structures for each mandrel. Similarly, self-aligned triple and quadruple patterning techniques are known. Multiple patterning techniques generally include the use of multiple masking steps. The first step may be called the mandrel mask and the second step may be called the block mask. Together, the two masking steps form the desired pattern.
For the smallest pitches self-aligned quadruple patterning (SAQP) may be utilized. SAQP based trench patterning process functions with an area selective blocking process where the infinite lines are cut into chains or line ends cut, et cetera, to form the final desired trench layout. As pitches get smaller, the overlay requirements of the block pattern go beyond the overlay capability of the lithographic tools.
It would be desirable to provide a multiple patterning process integration technique that reduces the overlay requirements of the process.